Grate elements of a grate consisting of grating stages which overlap like roof tiles and which can move relative to each other, which are constructed of one or more grate elements lying adjacent to each other, are subjected to high and widely varying heat demands, a high degree of mechanical abrasion, and chemical attacks. The wearing of a grate element depends to a great degree on the heat demands, so that in recent times fluid-cooled grate elements have been introduced, since fluid cooling is expected to provide better cooling and a more even temperature distribution within the grate element.
From European Patent A-0 621 449 a plate-shaped grate element is known which is executed as a hollow body of sheet metal, and which has an inlet and an outlet for cooling water. With this known grate element it is also possible to provide baffles in the hollow body in order to force the cooling water to flow through the grate element in an indirect path. The inlet and outlet are placed in the area of the attachment or drive end of the grate element. With a grate element constructed in this way there are very large flow profiles and associated dead spaces, flow interruptions, and irregular distributions of the cooling fluid. In addition, such grate elements cannot be adequately vented, so that rather large accumulations of air can form, which lead to significantly poorer cooling in this area and hence to overheating of the grate element. This is particularly detrimental when the grate elements are deployed in a reverse pusher grate, where the grate element heads are located at a higher position than the respective attachment or drive end of the grate element due to the inclined installation position. With such an installation position, the air which is present in the grate element then collects in the head area of the grate element, which is in principle subjected to greater heat demands, independently of the type of grate, so that in combination with the poorer cooling effect brought about by air bubbles the wearing of the grate element rises sharply. Furthermore, the grate elements which are in the form of hollow sheet metal bodies can warp under uneven cooling and thereby lead to malfunctions in the operation of the grate. The deployment of the inlet and outlet for the cooling fluid in the rear area of the grate element, i.e. in the vicinity of the attachment or drive end, leads to unsatisfactory reading of the coolant temperature, since the inlet and outlet locations are in the cooler area and it is practical to apply temperature probes to the outlet. The problems of overheating due to air bubbles, explained earlier, especially in the area of the head, can therefore not be recognized adequately.
From German Patent C-44 00 992 a fluid-cooled grate bar is known which has at least one conduit, the sections of which run parallel to each other in the longitudinal direction of the grate bar and are connected with a reverser in the head area of the grate bar. The inlet and outlet for this conduit are in the rear area for this known grate bar as well, i.e. in the area of the attachment or drive end, so that here again basically similar disadvantages occur as in the case of the plate-shaped grate element which was mentioned first. With this known grate element too, which has a conduit with a substantially rectangular cross section and a folding course for changing the direction in the area of the head, flow interruptions or eddies and air accumulations cannot be avoided with certainty. Since in addition to the inlet the outlet is also deployed in the rear area of the grate bar, not only is the reading of the temperature inadequate, as already described, but also venting, that is the removal of any bubbles which may have formed in the head area, turns out to be extremely difficult.
The object of the invention is to design a grate element with fluid cooling of the type indicated above in such a way that an intended cooling of the grate element, adapted to the particular circumstances, can be achieved with little engineering effort and expense for control technology.